Electronically commutated internal rotor motor

ABSTRACT

An electronically commutated internal rotor motor ( 20 ) has an outer stator ( 28 ) and a permanent magnet rotor ( 36 ) arranged rotatably therein by means of a shaft ( 40 ) supported at its drive end ( 42 ) by a rotary bearing ( 54 ) located in the A-side bell ( 26 ) and supported at its other end ( 44 ) by a rotary bearing ( 72 ) located in the B-side bell ( 66 ). The rotary bearing ( 54 ) in the A-side bell is preferably so configured that it permits a small radial movement ( 56 ) of the drive end ( 42 ) relative to this bell ( 26 ). The rotary bearing ( 72 ) in the B-side bell ( 66 ) has its outer race ( 72 ) tensioned against a shoulder ( 90, 94 ). Its inner race ( 74 ) is tensioned between a shoulder ( 78 ) of the shaft ( 40 ) and a shaped part of non-ferromagnetic material. This shaped part is pressed by a countersunk screw ( 82 ), screwed into a threaded bore ( 84 ) of the other shaft end ( 44 ), against the inner race.

CROSS-REFERENCE

[0001] This application is a section 371 of International ApplicationPCT/EP03/00249, filed 14 Jan. 2003 and published in German as WO03-069765-A1 on 21 Aug. 2003. The priority of German application DE 20202 523.3 of 18 Feb. 2002 is claimed in the International Application.

FIELD OF THE INVENTION

[0002] The invention relates to an electronically commutated internalrotor motor. Such motors have a low axial moment of inertia (GD²) andare primarily used in situations where a high rotational acceleration ofthe rotor is required.

SUMMARY OF THE INVENTION

[0003] It is an object of the invention to provide a new electronicallycommutated internal rotor motor. In accordance with the invention, thisobject is achieved by supporting the ends of the rotor shaft in bearingsin an A-side bell and in a B-side bell, respectively, and providing atensioning element for the bearing in the B-side bell. One therebyobtains a robust motor, which enables, even at high accelerations, quietrunning of the motor and associated gears, and which is particularlyadapted for drives with high RPM which, during operation, are subject toloading by impacts and the like.

[0004] A preferred refinement of the invention is to mount a controlmagnet, for triggering commutation of the motor, in a recess of a shapedpart, of non-ferromagnetic material, located at one shaft end. Thismakes it possible to so arrange a control magnet, that its magneticfield is not influenced or only minimally negatively influenced by theshaped part and by the countersunk screw, so that exact commutation ofthe currents in the motor can be carried out by means of such a controlmagnet.

[0005] Further details and advantageous refinements of the inventionwill be apparent from the embodiment described in the followingdescription and drawings, which is not to be understood as a limitationof the invention.

BRIEF FIGURE DESCRIPTION

[0006]FIG. 1 is a longitudinal section through a preferred embodiment ofa motor according to the invention; and

[0007]FIG. 2 is an enlarged view of a portion of FIG. 1, with componentsseparated.

DETAILED DESCRIPTION

[0008]FIG. 1 illustrates an electronically commutated internal rotormotor 20 with a housing 22 having a cylindrical housing part 24, anA-side bell 26, and a mounting flange 29.

[0009] Inside cylindrical housing part 24 is arranged the laminationstack of an outer stator 28, whose winding heads are designated 30 and32. Stator 28 has an internal recess 34, in which a rotor 36, withpermanent magnets 38 on a shaft 40, is arranged. Its drive end isdesignated 42 and its inner shaft end is designated 44. Such a motor canalso be called a “permanently excited synchronous internal rotormachine.”

[0010] In the A-side bell 26, a seal 46 for the shaft 40 is provided, inthe usual manner. Also located there is a recess 48 in which is secureda guide ring 50, which receives in a slot-like recess, withslight-radial play, the outer race 55 of a rotary bearing 54. Thisradial play is indicated at 56. In other words, rotary bearing 54permits a slight radial movement of drive end 42 relative to A-side bell26. For this purpose, the outer race 55 is subjected to a radial forcein the direction of arrow 58 by a spring, not shown. The radialmovability generally approximates a fraction of a millimeter, e.g. 0.4mm, and serves to keep the play in a spiral or worm drive, driven byshaft 40, as small as possible. Particularly at high speeds exceeding10,000 RPM, a preferred field of application for such motors, noiseminimization in a drive system driven by the motor is very important.The inner race 60 of rotary bearing 54 is pressed onto the shaft 40.

[0011] In the open end of cylindrical housing part 24, a B-side bell 66is secured. This is formed with a recess 68, having an annular shoulder67 (FIG. 2) to receive the outer race 70 of a rotary bearing 72 whichpermits a slight cardanic movement of the right, inner shaft end 44, theinner race 74 of the bearing being secured on this end 44. For thispurpose, shaft 40 has an annular flange 78, with whose right shoulderthe shaft abuts against the left side of inner race 74. Against theright side rests a shaped part 80, which is essentially annular and isurged by the countersunk head 81 of a countersunk screw 82 in thedirection of shaft 40. Screw 82 is screwed into an internal thread 84 inshaft end 44, and thereby urges shaped part 80 in the direction of shaftend 44.

[0012] For assured holding-in of outer race 70, there is provided aflat, washer-shaped part or tensioning element 90 which is secured byits outer periphery onto bell 66 by a plurality of screws 92, preferablythree evenly distributed screws. A radially inner portion 94 of part 90engages against outer race 70 and urges it leftward against shoulder 67,recess 68 being somewhat narrower than outer race 70.

[0013] Screw 82 is here a countersunk screw with an inner hexagonalrecess 83. Shaped part 80 is composed of a non-ferromagnetic material,preferably brass. It has a cylindrical recess 100, whose bottom isdesignated 102 and is either flush with the upper surface 104 ofcountersunk screw 82, shown in FIG. 2, or slightly higher than this. Asshown, shaped part 80 is formed with a recess 106 complementary to head81, so that a compact structure results.

[0014] After shaped part 80 is secured with screw 82 onto shaft end 44,a control magnet 110 is secured in cylindrical recess 100, e.g. bygluing. FIG. 2 show the control magnet before the securing, while FIG. 1shows it afterward. Control magnet 110 is provided, on the upper surface111 shown in FIG. 2, with a magnetization pattern. In FIG. 2, its usefulflux 113 is designated 113, while its stray flux is designated 115.Useful flux 113 serves for control of magnetoresistive resistors 112,which are arranged on a housing cover 117 on the B-side of motor 22, asshown schematically in FIG. 1. They serve for detection of therotational position of rotor 36, in order to exactly control thecommutation of the currents in stator 28. Commutation by means of suchrotational position sensors 112 controlled by a control magnet 110 isknown, in many variations, to those skilled in the art, and thereforerequires no further explanation. Sensor 112 is preferably arranged in aspace defined as a theoretical axial geometric projection of thecontrol-magnet-adjacent end of shaft 40. Preferably, the magnetizationpattern on side 111 of control magnet 110 is first created, aftercontrol magnet 110 is secured in the recess 100, and this preferablyoccurs simultaneously with the magnetization of the permanent magnets 38of rotor 36.

[0015] The fact, that shaped part 80 is made of a non-ferromagneticmaterial, means that it causes no significant attenuation of controlmagnet 110, so that, even with a small control magnet 110, one obtains asufficiently strong useful flux 113. The use of magnetoresistiveresistors 112 is advantageous in this design, since such resistors areeven controllable by magnetic fields 113 which run transverse to theresistors 112. This structure is thus particularly well adapted forhigh-RPM motors and is also insensitive to axial impacts which, duringoperation, could exert their influence upon shaft 40. However, the useof other kinds of rotor position sensors is not excluded, e.g. Hallsensors or optical sensors.

[0016] The construction with the shaped part 80 and with the countersunkscrew 82 has proven to be advantageous, since one can use a screw 82 offerromagnetic material, which in this case performs as a part of themagnetic circuit of control magnet 110 and strengthens its useful flux113. The use of a screw head 81 with internal hexagon 83 is advantageousbecause the head forms a part of the magnetic circuit, and a symmetricalform of the magnetic circuit for the control magnet 110 so thereby avery exact commutation of the currents in stator 28 results, which,particularly at high RPM, is very important in order to obtain a maximalmotor power.

[0017] Naturally, many variations and modifications are possible, withinthe scope of the present invention.

1. An electronically commutated motor (20), comprising: an external stator (28); an A-side bell (26) provided on a drive side of the motor (20); a B-side bell (66) on an opposing side of the motor (20); a permanent magnet rotor (36) rotatably arranged in the external stator (28); a shaft (40) associated with the permanent magnet rotor (36) provided with a shoulder (78) and supported at its drive end (42) by a rotary bearing (54) in said A-side bell (26) and supported at a second shaft end (44) by a rotary bearing (72) arranged in said B-side bell (66); a tensioning element (90, 94) secured to said B-side bell (66), tensioning an outer race (70) of the rotary bearing (72) there between said tensioning element and a shoulder (67) of the B-side bell (66); a shaped part (80) composed of non-ferromagnetic material; a countersunk screw (82) screwed into an internal thread (84) of the other shaft end (44) which screw, via the shaped part, presses the inner race (74) of the rotary bearing located in the B-side bell (66) against a shoulder (78) of the shaft (40).
 2. The motor according to claim 1, wherein said shaped part (80) composed of non-ferromagnetic material is provided with a recess (100, 102), and a control magnet (110) is arranged in said recess, for controlling commutation of said motor.
 3. The motor according to claim 1, wherein the rotary bearing (54) in the A-side bell (26) is configured to permit a slight radial movement of said drive end (42) of said shaft (40), relative to said A-side bell (26).
 4. The motor according to claim 17, wherein the head (81) of the countersunk screw (82) forms a part of the magnetic circuit of the control magnet (110).
 5. The motor according to claim 1, wherein, in a space defined as a theoretical axial geometric projection of the shaft end opposite the control magnet (110), a galvanomagnetic sensor (112) is arranged, along with at least one magnetoresistive resistor controllable by a magnetic field (113) of the control magnet (110).
 6. The motor according to claim 1, wherein the outer race (70) of the rotary bearing (72) in said B-side bell (66) is somewhat longer than a recess (68) which receives said outer race, and wherein a tensioning element in the B-side bell (66) is formed as an essentially flat metal part which engages with its inner periphery (94) against said outer race (70) and which, in a region of its external periphery, is secured with screws (92) to the B-side bell (66).
 7. The motor according to claim 1, wherein the rotary bearing (72) arranged in the B-side bell (66) is so formed that it permits a cardanic movement of the shaft (40) supported in the bearing.
 8. The motor according to claim 2, wherein the rotary bearing (72) arranged in the B-side bell (66) is so formed that it permits a cardanic movement of the shaft (40) supported in the bearing.
 9. The motor according to claim 3, wherein the rotary bearing (72) arranged in the B-side bell (66) is so formed that it permits a cardanic movement of the shaft (40) supported in the bearing.
 10. The motor according to claim 4, wherein the rotary bearing (72) arranged in the B-side bell (66) is so formed that it permits a cardanic movement of the shaft (40) supported in the bearing.
 11. The motor according to claim 5, wherein the rotary bearing (72) arranged in the B-side bell (66) is so formed that it permits a cardanic movement of the shaft (40) supported in the bearing.
 12. The motor according to claim 6, wherein the rotary bearing (72) arranged in the B-side bell (66) is so formed that it permits a cardanic movement of the shaft (40) supported in the bearing.
 13. The motor according to claim 2, wherein the outer race (70) of the rotary bearing (72) in said B-side bell (66) is somewhat longer than a recess (68) which receives said outer race, and wherein a tensioning element in the B-side bell (66) is formed as an essentially flat metal part which engages with its inner periphery (94) against said outer race (70) and which, in a region of its external periphery, is secured with screws (92) to the B-side bell (66).
 14. The motor according to claim 3, wherein the outer race (70) of the rotary bearing (72) in said B-side bell (66) is somewhat longer than a recess (68) which receives said outer race, and wherein a tensioning element in the B-side bell (66) is formed as an essentially flat metal part which engages with its inner periphery (94) against said outer race (70) and which, in a region of its external periphery, is secured with screws (92) to the B-side bell (66).
 15. The motor according to claim 4, wherein the outer race (70) of the rotary bearing (72) in said B-side bell (66) is somewhat longer than a recess (68) which receives said outer race, and wherein a tensioning element in the B-side bell (66) is formed as an essentially flat metal part which engages with its inner periphery (94) against said outer race (70) and which, in a region of its external periphery, is secured with screws (92) to the B-side bell (66).
 16. The motor according to claim 5, wherein the outer race (70) of the rotary bearing (72) in said B-side bell (66) is somewhat longer than a recess (68) which receives said outer race, and wherein a tensioning element in the B-side bell (66) is formed as an essentially flat metal part which engages with its inner periphery (94) against said outer race (70) and which, in a region of its external periphery, is secured with screws (92) to the B-side bell (66).
 17. The motor according to claim 1, wherein a head (81) of the countersunk screw (82) is provided with an internal hexagon (83) for its actuation.
 18. The motor according to claim 2, wherein a head (81) of the countersunk screw (82) is provided with an internal hexagon (83) for its actuation.
 19. The motor according to claim 18, wherein the head (81) of the countersunk screw (82) forms a part of the magnetic circuit of the control magnet (110). 